rs1154155 is a SNP in the TCRA T-cell receptor alpha gene. The minor allele is (G).

A study of 1,830 people with narcolepsy and cataplexy (a sudden loss of muscle tone that can cause people to collapse) compared to 2,164 healthy controls concluded that several SNPs in the TCRA gene were linked. The most significant association was with this SNP, rs1154155, with an
average allelic odds ratio of 1.69 (genotypic odds ratios 1.94 and 2.55, p < 10e-21).[PMID 19412176]

Note the following, though, as quoted from a Science News article: "Even with all of the known genetic risk factors, including the newly discovered version of the T cell receptor gene, a person has only a 1.5 percent chance of developing narcolepsy.... That suggests that, while narcolepsy is probably an autoimmune disorder, further genetic and environmental triggers and risk factors remain to be found."